Can optical modules replace copper cables

Copper cables will not fully replace optical modules; instead, both technologies are expected to coexist, with copper dominating short-range connections inside racks and optical modules handling long-distance interconnects.

Current Role of Copper and Optical Modules

Copper cables remain indispensable for short-distance, high-speed connections within server racks due to their low latency, zero power consumption, and high reliability. Nvidia CEO Jensen Huang emphasized that inside AI server racks, copper cables are critical for scale-up configurations, particularly for distances under 2 meters, where optical modules would generate excessive heat from electro-optical conversion, complicating cooling systems and energy efficiency . Optical modules, on the other hand, excel in long-distance interconnects between racks or across data center campuses. They provide higher bandwidth, immunity to electromagnetic interference, and lower signal loss over longer distances, making them essential for scale-out architectures and AI clusters that span multiple racks or buildings .

Advantages and Limitations

Copper cables:

• Excellent for ultra-short reach (<2–3 meters) due to low latency and minimal power overhead .
• Cost-effective and simple to deploy within existing rack infrastructure .
• Limited by skin effect, EMI, and thermal challenges at higher frequencies or longer distances . Optical modules:
• Provide higher bandwidth and lower bit error rates over long distances .
• Immune to electromagnetic interference, enabling cleaner signal transmission .
• Require precise fabrication, alignment, and thermal management, making them more expensive and complex for short-range applications .

Emerging Trends

• Co-Packaged Optics (CPO) is gaining traction for high-density, energy-efficient interconnects in AI-scale GPU clusters. CPO shortens electrical trace lengths and reduces power consumption, offering a hybrid approach that leverages both copper and optical technologies .
• “Coherent-lite” optics are being developed for 10–40 km interconnects between data center buildings, complementing copper in a broader optical hierarchy .
• Industry forecasts suggest that while optical adoption will grow rapidly in back-end and long-distance links, copper usage inside racks will remain significant at least until 2027, with large-scale optical penetration inside racks expected around 2028 .

Conclusion

Copper cables are not being replaced outright by optical modules. Instead, the future of data center interconnects is a dual-era model where copper handles short-range, high-density connections inside racks, and optical modules manage long-distance, high-bandwidth links. This coexistence allows data centers to balance performance, energy efficiency, and cost, while gradually integrating optical technologies where they provide the most advantage .